JP4519973B2 - Pneumatic tire - Google Patents

Description

【００３０】
表１より明らかな如く、本発明に適合する供試タイヤは、従来タイヤに比較してビード部の耐久性が格段に改善されることが確認できた。
【００３１】
【発明の効果】
本発明によれば、カーカスプライの巻き返し部分に、ビードコアの周面に沿ってそれに巻き付く巻き込み部を有する空気入りタイヤにおいて、硬ゴムを備えたゴムチェファ配設することによって、プライコードの引き抜けやカーカスプライ巻き返し部分のセパレーションを、より有利に回避してビード部の耐久性を大きく向上させることができる。
【図面の簡単な説明】
【図１】本発明の実施の形態を示す要部横断面図である。
【図２】本発明の他の実施の形態を示す要部横断面図である。
【図３】本発明の他の実施の形態を示す要部横断面図である。
【図４】巻き込み部の先端位置を示すビードコアの拡大断面図である。
【図５】実施例で用いた供試タイヤの要部横断面図である。
【図６】実施例で用いた供試タイヤの要部横断面図である。
【図７】（ａ）（ｂ）は従来のビード部構造を例示するタイヤの要部用断面図である。
【図８】（ａ）（ｂ）はビード部クラックの発生態様を示す横断面図である。
【符号の説明】
１ トレッド部
２ サイドウオール部
３ ビード部
４ ビードコア
５ スティフナ
６ カーカスプライ
７ 巻き返し部
８ ワイヤチェファ
９ カーカスプライ
10 ワイヤチェファ
11 ビードコア
12 ゴムスティフナ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire particularly suitable for heavy loads such as trucks and buses, and relates to a bead portion structure with improved durability that suppresses occurrence of separation of ply cords and separation of a carcass ply winding portion. It is about improvement.
[0002]
In heavy-duty pneumatic tires with a large rolling load on the tire, there is concern about pulling out of the ply cord.Therefore, the carcass ply is largely wound from the radial direction of the tire to the outside around the bead core of the bead portion. The rewinding part is embedded and fixed in rubber.
[0003]
7A and 7B are schematic cross-sectional views of the bead portion illustrating this, and FIG. 7A shows the outer end of the rewinding portion 9a of the carcass ply 9 and the same outer portion of the wire chafer 10. FIG. 7B shows a structure in which the rewinding outer end of the wire chafer 10 is positioned radially outward of the tire from the outer end of the rewinding portion 9a of the carcass ply 9 from the end. belongs to.
[0004]
[Problems to be solved by the invention]
By the way, in such a conventional bead structure, there is a rigidity step on the inner and outer sides in the radial direction of the tire with the outer end position of the carcass ply 9 being wound or the outer end position of the wire chafer 10 as a boundary. When the load rolling is repeated, stress is concentrated in the vicinity including the outer end of the carcass ply 9 or the outer end of the wire chafer 10 due to repeated deformation from the bead portion to the side wall portion.
[0005]
This causes separation from the rubber at the outer end, and this separation further causes a bead crack cr as shown in FIGS. 8 (a) and 8 (b).
[0006]
Therefore, the purpose is to relieve the stress generated at the outer end of the turn-up portion of the carcass ply 9 or the outer end of the wire chafer 10 and the vicinity thereof, and also increase the rigidity of the bead portion to suppress deformation of the bead portion. In addition, a plurality of organic fiber cord layers are arranged around the bead core 11 so as to circumscribe the wire chafer 10, and these organic fiber cord layers cover the outer end of the carcass ply 9 or the outer end of the wire chafer 10. The rubber stiffener 12 disposed between the main body portion of the carcass ply 9 and the rewinding portion 9a on the outer side in the tire radial direction of the bead core 11 has been devised such as increasing the amount of hard rubber stiffener. According to the above, when the heat generation temperature of the bead portion in the load rolling of the tire is further increased, In addition to the generation of Deployment, also there is a problem that separation occurs in the outer end of the organic fiber cord layer, other weight increase and tire productivity tire is lowered.
[0007]
An object of the present invention is to solve the above-described problems of the prior art, and the object of the present invention is to provide a carcass ply and a carcass ply without causing an increase in tire weight and a decrease in tire productivity. The present invention proposes a pneumatic tire that can effectively prevent separation of the outer end of the wire chafer from the rubbery material, and can sufficiently prevent the ply cord from being pulled out and can greatly improve the bead durability.
[0008]
[Means for Solving the Problems]
In the pneumatic tire of the present invention, at least one carcass ply made of a steel cord extends to a toroidal from a tread portion to a bead portion through a side wall portion, and adjacent to the bead core embedded in each bead portion. A pneumatic tire having a winding portion wound around the circumference of the bead core at each winding portion of the carcass ply along the circumference of the rubber stiffener. ,
The rubber stiffener is at least partially made of hard rubber, and the hard rubber has a modulus (M o ) at 50% elongation of 5.5 MPa ≦ M o ≦ 7.0 MPa ,
The winding portion is provided with at least one plastic deformation portion corresponding to a cross-sectional contour shape of the bead core, and the winding portion of the winding portion is sandwiched and restrained only by the bead core and the rubber stiffener. It is a pneumatic tire.
[0009]
Here, in the rubber stiffener, the ratio (S / S ₁ ) of the cross-sectional area of the hard rubber (S ₁ ) to the total cross-sectional area (S) of the stiffener 5 is in the range of 30% ≦ S ₁ / S ≦ 100%. It is desirable to satisfy
[0010]
In addition, such a rubber-fifter has a rim assembly posture of a tire filled with air pressure, and has a height H ₂ from the lowermost winding end of the carcass ply to the uppermost end of the hard rubber in the rubber stiffener and the lowermost winding end of the carcass ply from the lowermost winding end of the carcass ply. It is preferable that the ratio to the height H ₁ up to the uppermost end of the lens satisfies the condition of 10% ≦ H ₂ / H ₁ ≦ 70%.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described more specifically with reference to the drawings.
FIG. 1 is a cross-sectional view of a tire showing an embodiment of the present invention, in which 1 is a tread portion, 2 is a side wall portion continuous to the tread portion 1, and 3 is a bead portion. 3 is continuous with the radially inner peripheral side of the side wall portion 2, and a bead core 4 having a cross-sectional shape of, for example, a hexagonal shape and a stiffener 5 disposed adjacent to the bead core 4 are embedded in the bead portion 3. . The stiffener 5 includes a normal rubber 5 a and a hard rubber 5 b, and the hard rubber 5 b is disposed between the rubber 5 a and the bead core 4.
[0012]
Reference numeral 6 denotes a carcass ply. The carcass ply 6 extends at an angle of substantially 90 ° with respect to the equator plane of the tire, for example, a steel cord (strength: in the range of 80 to 300 kgf, more preferably A ply cord can be applied, and a single carcass ply 6 made of this ply cord can be extended toroidally from the tread portion 1 through the side wall portion 2 to the bead portion 3. At the same time, it is wound around the bead core 4 and the stiffener 5 from the inner peripheral side to the outer peripheral side in the radial direction of the tire.
[0013]
As shown in FIG. 1 above, the carcass ply 6 is turned back from the outer side in the width direction of the tire as shown in FIG. The winding part 7 of the carcass ply 6 has a winding part 7 a that winds along the peripheral surface of the bead core 4 in any of these.
[0014]
With respect to the winding part 7 a shown in FIG. 1 or FIG. 2, both correspond to the cross-sectional contour shape of the bead core 4 in the portion corresponding to the winding part 7 a before the carcass ply 6 is wound around the bead core 4. In advance, at least three plastic deformation portions P ₁ , P ₂ , and P ₃ are provided. In particular, at the front end P ₁ , the bead core 4 is sufficiently close to the peripheral surface of the bead core 4 and accurately copied to the bead core 4. It shall be wrapped.
[0015]
The winding portion 7a extends along the peripheral surface of the bead core 4 over a half circumference of the cross-sectional contour of the bead core 4, for example, the bead core 4 on the side of the bead base 3a. In particular, the winding portion 7a as shown in FIG. In addition to this, the tip of the tire is assumed to be positioned inward of the tire width direction beyond the position of the outer peripheral edge of the bead core 4 in the tire rim assembly posture filled with air pressure.
[0016]
In the pneumatic tire configured as described above, the winding portion 7a is provided in the rewinding portion 7, so that the pull-out of the ply cord is effectively prevented, and at the same time, under the action of the bead core 4 and the rim R. The separation of the winding part 7 can be effectively avoided.
[0017]
In the present invention, the hard rubber 5b is used for the rubber stiffener 5, but this increases the rigidity of the upper portion of the bead portion 3 and suppresses the falling of the bead portion 3 when a load is applied, thereby improving the bead durability. Contribute to.
[0018]
In particular, the modulus M at 50% elongation of the hard rubber 5b o is as defined 5.5 MPa ≦ M o ≦ 7.0MPa, because the bead portions 3 modulus M o is lower than 5.5MPa This is because it is not possible to expect the effect of suppressing the falling of the material, and on the other hand, when it is higher than 7.0 MPa, destruction is likely to occur from such a part.
[0019]
In the rubber stiffener 5, the ratio (S ₁ / S) of the cross-sectional area (S ₁ ) of the hard rubber 5b to the total cross-sectional area (S) of the rubber stiffener 5 is 30% ≦ S ₁ / S ≦ 100%. It is preferable to be within the range. The reason is that when (S ₁ / S) is a value lower than 30%, there is a possibility that the hard rubber 5b may be broken from the site. For improving the durability of the bead part 3, the above range is used. It is because it is the best to prescribe.
[0020]
As shown in FIG. 1 above, the rim assembly posture of the tire filled with air pressure leads from the lowermost winding end L ₁ of the carcass ply 6 (from the bead base 3a side of the bead core 4) to the most advanced L ₂ of the hard rubber 5b. the ratio between the height H ₁ up to the uppermost L ₃ of the carcass ply 6 from a height rewinding lowermost end L ₁ of H ₂ and the carcass ply 6 until a _{10% ≦ H 2 / H 1} ≦ 70% Is preferred. The reason is that when (H ₂ / H ₁ ) is less than 10%, the effect of using the hard rubber 5b is small, while (H ₂ / H ₁ ) exceeds 70%. This is because stress tends to concentrate on the tip of the stiffener 5 and there is a concern about the occurrence of separation.
[0021]
FIG. 3 is an example in which the wire checker 8 is disposed around the bead core 4 so as to circumscribe the carcass ply 6. In the case of such a configuration, the deformation amount at the outer end and in the vicinity of the part is shown. Therefore, separation of the outer end of the wire chafer 8 can be effectively reduced.
[0022]
By sandwiching the winding portion 7 between the bead core 4 and the stiffener 5, it becomes possible to increase the restraining force on the winding portion 7 and to prevent the ply cord from being pulled out more advantageously.
[0023]
FIG. 4 shows an enlarged cross section of the bead core 4. In order to ensure the effect of preventing the pull-out of the ply cord in the pneumatic tire, it is preferable that the tip of the winding portion 7 is positioned on any of the three sides a, b, c away from the bead base 3a. Preferably, the arrangement range is a range of 2/3 of the length of each side from the intersection position of the side a and the side b.
[0024]
In the present invention, the plastic deformation portions P ₁ , P ₂ , and P ₃ can be provided in the entrainment portion 7 as described above. However, one or two places may be provided, and four places may be provided as necessary. It is also possible.
[0025]
【Example】
Below, the Example regarding the drum durability of the tire which concerns on this invention is described.
[0026]
The test tire used was a tire having a structure as shown in Table 1 and having a size TBR285 / 60R22.5 mounted on a rim of 9.00 × 22.5.
[0027]
Drum durability is determined by filling the rim-assembled tire with the maximum air pressure (900 kPa) and testing the bead failure (separation at the ply end or wire chafer end) in a running test on the drum with a load equivalent to twice the maximum load capacity. ) Or the distance traveled when the vehicle could not run due to a rubber chafer crack or the like, and evaluated by indexing the conventional tire as a control. It should be noted that the drum durability is more excellent as the index value is larger.
[0028]
The results are shown in Table 1. FIG. 5 shows a cross section of the main part of the tire including the rubber stiffener 5 in which the hard rubber area ratio is 30%, and FIG. 6 shows that the hard rubber area ratio is 100%. The cross section of the principal part of the tire provided with the rubber stiffener 5 is shown.
[0029]
[Table 1]

[0030]
As is clear from Table 1, it was confirmed that the test tire conforming to the present invention has a marked improvement in the durability of the bead portion as compared with the conventional tire.
[0031]
【The invention's effect】
According to the present invention, in a pneumatic tire having a winding portion wound around a bead core along a circumferential surface of a bead core at a winding portion of a carcass ply, by disposing a rubber chafer provided with hard rubber, the ply cord can be pulled out. The separation of the carcass ply rewinding portion can be avoided more advantageously, and the durability of the bead portion can be greatly improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a main part showing an embodiment of the present invention.
FIG. 2 is a cross-sectional view of an essential part showing another embodiment of the present invention.
FIG. 3 is a cross-sectional view of an essential part showing another embodiment of the present invention.
FIG. 4 is an enlarged cross-sectional view of a bead core showing a tip position of a winding portion.
FIG. 5 is a cross-sectional view of an essential part of a test tire used in an example.
FIG. 6 is a cross-sectional view of an essential part of a test tire used in an example.
FIGS. 7A and 7B are cross-sectional views for a main portion of a tire illustrating a conventional bead portion structure. FIGS.
FIGS. 8A and 8B are cross-sectional views showing a form of occurrence of a bead crack. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Bead core 5 Stiffener 6 Carcass ply 7 Rewind part 8 Wire chafer 9 Carcass ply
10 Wire Cheffer
11 Beadcore
12 Rubber stiffener

Claims (3)

At least one carcass ply made of a steel cord extends to the toroidal from the tread portion to the bead portion through the sidewall portion, and along the bead core embedded in each bead portion and the rubber stiffener adjacent thereto, A pneumatic tire having a winding portion wound around the bead core along the circumferential surface of the bead core at each winding portion of the carcass ply from the inner circumferential side to the outer circumferential side in the radial direction of the tire,
The rubber stiffener is at least partially made of hard rubber,
The hard rubber has a modulus (M o ) at 50% elongation of 5.5 MPa ≦ M o ≦ 7.0 MPa ,
The winding portion is provided with at least one plastic deformation portion corresponding to a cross-sectional contour shape of the bead core, and the winding portion of the winding portion is sandwiched and restrained only by the bead core and the rubber stiffener. Pneumatic tire. In the rubber stiffener, the ratio (S ₁ / S) of the cross-sectional area of the hard rubber (S ₁ ) to the total cross-sectional area (S) of the rubber stiffener satisfies the range of 30% ≦ S ₁ / S ≦ 100%. The pneumatic tire according to claim 1, which is a tire. The rubber edge is a tire rim assembly posture filled with air pressure, the height H ₂ from the lowest end of the carcass ply rewinding to the foremost end of the hard rubber and the lowest end of the rewinding of the carcass ply to the uppermost end of the carcass ply The pneumatic tire according to claim ₁ , wherein a ratio (H ₂ / H ₁ ) to a height H ₁ of the tire is 10% ≦ H ₂ / H ₁ ≦ 70%.

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